These culture vessels are made to exacting tolerances in order to provide higher cell yields. The glass is specially selected for optical clarity, interior surface smoothness, and the absence of glass imperfections. The neck area is tapered for easy cleaning and removal of cells. Glass wall thickness is 2.6 mm. The wider opening vessels provide easier access to the inside for removing cells or cleaning. These vessels are made of Wheaton 33 low extractable borosilicate glass that conforms to USP Type I and also ASTM E-438 Type I, Class A requirements.